I first heard about Salò from an Italian professor who quickly cautioned, "Do not watch it. Ever." Naturally that made me seek it out faster. For those who haven't seen it — or haven't read the book by the Marquis de Sade — the Pasolini film focuses on a group of fascists who kidnap, torture, and sexually abuse 18 teenagers. The most repulsive scene involves coprophagy. And this time, I must warn you: DO NOT LOOK IT UP.

We usually think of musicals as escapist entertainment, but that's not the case with Dancer in the Dark, which is the bleakest musical you will ever endure. If the ending doesn't leave you feeling completely empty, you might be dead inside. Björk stars as a blind Czech immigrant who has to do terrible things to pay for surgery that will save her son's sight. Things do not end well for her, or for the audience.

This psychological thriller has been remade (both by its director Michael Haneke and as obvious rip-offs), but the original is still the hardest to watch. Why do the two young men take a family hostage and torture them with sadistic games? Unclear! That makes it so much worse — as do the direct addresses to the audience, reminding you that you're taking part in the voyeuristic thrills.

Commonly regarded as the most depraved movie of all time, A Serbian Film is horrifying enough that even reading the Wikipedia description will leave you feeling dirty for days. Suffice it to say the plot involves a porn star tricked into making a snuff film, complete with necrophilia and horrible things done to children. Steer clear. Those who have seen it say it's not worth the trauma.

Kids, don't do drugs. But mostly, don't watch Requiem for a Dream. Darren Aronofsky's disturbing look into addiction has his characters completely lose themselves in a drug-induced haze — only to wake up to a reality most of us can't even imagine. The final scenes are so dark and upsetting that you'll need to take a long, hot shower before feeling OK again.

Cannibal Holocaust is one of the earliest examples of found footage horror, and it still leaves a more lasting impression than almost all of the modern iterations. That's because it feels painfully real — so real, in fact, that director Ruggero Deodato was put on trial for making what appeared to be a snuff film. Warning: The violence against animals, including an ill-fated turtle, is almost certainly not faked.

The most distressing thing about The Woman isn't that a seemingly normal father kidnaps and tortures a feral woman — it's that his family goes along with it. And they continue to live almost normal lives, while periodically torturing the voiceless stranger in their cellar. As the film progresses, we realize how twisted these people are, but the divide between the psychotic and the matter-of-fact remains jarring.

There is an awful twist at the end of Oldboy: I won't spoil it for you, but it crawls under the skin and leaves you feeling nauseated long after the movie has ended. The film as a whole is brutal — such is usually the case with Korean crime thrillers — but it's that gut-punch of a conclusion that really leaves a mark. Just thinking about it makes me a little ill.

When a film has been parodied as often as Deliverance has, it's hard to take it seriously. But even knowing what's coming, the feeling of dread is pervasive. And the infamous rape scene is still brutal. The subsequent murders and attempts at a cover-up — yes, there's more to the movie than that one scene — are stark reminders of how little some people value life.

I survived the first Human Centipede, which was icky but entertaining. How much worse could the sequel be? Um. SO MUCH WORSE. This is truly one of the most revolting films I've sat through, and the only consolation is that it's filmed in black and white. That means that while you're still seeing an endless array of bodily fluids, you're spared knowing which is which. It's a really small consolation.

Roger Ebert once wrote that Irreversible is "a movie so violent and cruel that most people will find it unwatchable." Yeah, basically. There is little you can do to recover from a film with such a relentless rape scene, one that has been criticized for being exploitative, anti-woman, and — given the sexuality of the perpetrator — homophobic. And yet, some prize the movie as a contemporary classic.

There's something unnerving about young Jodie Foster, who picked roles that were always (intentionally) more adult than she was. This French Canadian film is no different, with Foster playing the titular girl with a very dark past. If that doesn't keep you up at night, there's a scene in which a hamster is tortured to death with a cigarette. Try not to think about it too much.

It's difficult to talk about why House of Sand and Fog is so devastating without giving away the ending. Here's what I will say: I cried for hours after suffering through a conclusion that is dark, depressing, and endlessly unfair. In fact, it's that sense of injustice that makes the movie such a distinct downer — it's more than just an exercise in emotional manipulation.

The rape-revenge genre is a tough one — for obvious reasons — and no film encapsulates it better than the original I Spit on Your Grave. Is it problematic? Sure. But it's also cathartic, if you're into watching horrible people getting what they deserve. You'll feel satisfied, but you won't feel good: because if the answer to violence is more violence, where does that leave us?

Long before Spring Breakers, Harmony Korine was making us fear young people with movies like Gummo, which offers a series of interconnected vignettes that are all pretty difficult to stomach. In particular, a man pimping out his sister with Down syndrome, and the repeated murder of cats. Lots of cats. It's a portrait of small-town American life that is as far from Norman Rockwell as you can get.

It's not just that I Saw the Devil is incredibly violent (it is, though, naturally). It's that once again we're forced to follow a "hero" who does terrible things, in this case to enact his revenge on the serial killer who murdered his pregnant fiancé. The murders themselves, though, are so beautifully shot that you feel forced to keep watching, against your better judgment.

The Mist isn't particularly violent, and its monsters (once we finally see them) are honestly a bit underwhelming. At the same time, the central focus is on people trapped inside a supermarket, and how quickly they devolve into mob mentality. You know what's scarier than the mist? HUMAN BEINGS. Combine that with the bleakest ending imaginable and you've got a truly upsetting film.

Because sometimes real life is more horrible than anything a Hollywood screenwriter can dream up. The slaughter of millions of Cambodians under the Khmer Rouge regime is unfathomably awful on its own. To see it realized in this acclaimed Academy Award–winning drama drives home the trauma: It's a stark reminder that images often speak louder than words.

The first Hostel might mess you up a bit, but it's really just OK — the sequel transcends the torture-porn genre with a look at people's darkest desires. Without giving too much away, we get to know the torturers a bit more in the second outing. It should probably come as no surprise that those who seem kindest on the surface are harboring the most depraved passions. Because everyone is terrible.

I've heard Dear Zachary described as a "descent into hell" and "the saddest documentary ever made." Both are pretty accurate. The less you know about the story, the better, because the building horror of this real-life drama is most effective when you don't see it coming. Just know that it will tear your heart out — and that you'll need at least an hour of racking sobs to recover.

Deadgirl takes the "boys will be boys" idiom to its horrifying conclusion. On one level, it's a clear condemnation of rape culture. On the other, it's just awful to sit through, as these teenagers drop all semblance of compassion in order to turn their pet zombie into a sex toy. The film never justifies their behavior, but seeing it is still enough to make you queasy.

Wes Craven's directorial debut isn't as gory as some of his later offerings, but it will keep you up at night much longer than Scream did. This is another rape-revenge movie, and it's one that gets the whole family involved. Watch as a seemingly normal couple turn bloodthirsty after their daughter is violated. Or don't watch, if you'd like to continue living in blissful ignorance.

Any number of Todd Solondz movies could fit on this list, but Happiness gets under your skin more than the rest. It's darkly comedic with an emphasis on dark — what most viewers remember is the scene where pedophile Bill tearfully admits to drugging and raping his son's friends. Philip Seymour Hoffman also stars in one of the most depressing Philip Seymour Hoffman roles ever. Which is saying something.

New French horror is known for being incredibly violent and disturbing, and Martyrs is no exception. Grisly torture aside, the slow comprehension of why these girls are being made martyrs just makes everything worse. The idea that they have to suffer for the greater good is so upsetting that it nearly trumps what they actually go through.

And Lars Von Trier makes another appearance — he's so good at completely destroying his audience. Antichrist is infamous for its graphic depictions of sexual violence, but the movie is so unsettling as a whole, those brutal moments feel almost secondary. Few other films have been as successful at capturing the unending nightmare of mourning.